Methods of delivering pharmaceutically active agents are desirable in a variety of applications. For example, to counter the adverse reactions that often accompany a medical implant or insert, pharmaceutically active agents have been applied to or embedded within medical devices. This can be accomplished, for example, by covering the surface with a coating containing the active agent. Accordingly, medical device coatings are known that release a pharmaceutically active agent via dissolution of the active agent or by cleavage of the active agent from the coating.
One approach to the incorporation of a pharmaceutically active agent into a polymeric network is to absorb the active agent into the coating from a solution. Hydrophilic polymers in contact with an aqueous solution of an active agent, such as by soaking the polymer in a solution of the active agent, will swell to contain the solution and absorb the active agent dissolved therein. Upon drying, the polymeric network includes the associated active agent. The use of such a polymeric network as a coating for a medical device allows for the association and immobilization of a water soluble active agent with and/or within the medical device. The active agent can then be released from the coating upon contact with aqueous body fluids.
Such polymeric networks can be biodegradable. For example, biodegradable hydrogels can be carriers for biologically active agents such as hormones, enzymes, antibiotics, antineoplastic agents, and cell suspensions. Proper choice of hydrogel macromers can produce membranes with a range of permeability, pore sizes, and degradation rates suitable for a variety of applications in surgery, medical diagnosis, and treatment.
Bioerodable polymers can also be used that include a pharmaceutically active agent as a subunit of the polymer. See, for example, U.S. Pat. Nos. 5,837,228 and 6,486,214.
Another approach to the association of a pharmaceutically active agent with a polymeric coating is by chemical attachment, e.g., covalent attachment, of the active agent to the coating. For example, coating compositions are known that include a nitric oxide-releasing functional group bound to a polymer. U.S. Pat. Nos. 5,676,963 and 5,525,357 disclose such polymeric coating compositions.
The discussion of prior publications and other prior knowledge does not constitute an admission that such material was published, known, or part of the common general knowledge. Although numerous such materials and methods of delivery of agents, particularly pharmaceutically active agents, are known, other methods and materials are still needed.